Self-destructive explosive cartridge for underwater seismic exploration



y 30, 1957 G. L. GRIFFITH ETAL 3,322,066

SELF-DESTRUCTIVE EXPLOSIVE CARTRIDGE FOR UNDERWATER SEISMIC EXPLORATION Filed Feb. 8, 1966 United States Patent 3,322,066 SELF-DESTRUCTIVE EXPLOSIVE CARTRIDGE FOR UNDERWATER SEISMIC EXPLORATION George L. Griffith, Coopersburg, and William L. K.

chwoyer and Stephen L. Mayer, Allentown, Pa., assignors to Trojan Powder Company, Allentown, Pa, a

corporation of New York Filed Feb. 8, 1966, Ser. No. 525,913 12 Claims. (Cl. 102-24) This invention is directed to an explosive cartridge such as a primer or booster especially intended for use in underwater seismic exploration, and which is selfdestroying after immersion in water.

A problem in underwater seismic testing or blasting is the booster, primer or other cartridge which for some reason does not detonate. An extremely hazardous situation sometimes occurs at the beachfront in coastal areas in the vicinity of intensive oil-shore oil drilling and exploration. Seismic explosive charges which fail to detonate may eventually rise to the surface and be washed up on shore where they may be accidentally detonated, causing damage or injury. Hence, it has been necessary to recover such cartridges and manually deactivate them.

The present invention provides an explosive cartridge such as a primer or booster which avoids this problem by means incorporated therein automatically to permit deactivation and destruction thereof by water even if the cartridge charge does not detonate within a predetermined period of time.

The explosive container in accordance with the invention exposes an explosive charge contained therein to water, after immersion in water, and comprises, in combination, a container defining a compartment, an opening in the container into the compartment for flow of water thereinto and for escape of water-insoluble material therefrom, after the cartridge is immersed in water, an explosive charge contained in the compartment, and in admixture therewith, an inert water-activatable dissipator which undergoes a change in volume when contacted with water and thus facilitates the circulation of water through the compartment, to aid in dispersing and inactivating the charge.

The dissipator can be water-soluble, and inert to the explosive charge, and thus is dissolved in water, and thereby reduces the volume of material in the compartment, there- 'by rendering it easier to distribute water-insoluble components of the charge into the water and out of the cartridge. Such a water-soluble material is itself not an explosive and should not react with or in any way affect the effectiveness of the explosive charge.

The dissipator can also react to evolve a gas upon being contacted with water, as it is thus consumed reducing the volume of material in the compartment to aid the passage of water therethrough and as well as evolving a gas to aid in distributing material out the opening into the water. If the evolution of was is brisk enough, it can also activate means operated by pressure in the container, to burst the container or force off an end cap, and thereby more quickly expose the entire charge to the deleterious and distributing action of the water.

A water-expandi-ble dissipator can be mixed with the explosive charge, and upon expansion in volume aids in forcing water-insoluble charge components out the openice ing, to expose them to the water. As the volume of solid or gas in the container is increased, either by swelling of the solid or by evolution of gas, the pressure required to operate such pressure-activatable means is eventually reached, causing the cartridge to open and expose the explosive.

The preferred type of dissipator is one which dissolves in water. Water-soluble materials which are inert to the charge and which do not themselves have any explosive properties include particulate polyvinyl, other watersoluble gums, such as gu'ar gum, soluble salts such as sodium chloride, calcium chloride, the alkali metal sulphates, the alkali metal chlorates, other water-soluble solid organic materials such as sugar, oxalic acid, tartaric acid, water-soluble starch, etc. Preferably, the watersoluble material will not substantially increase the viscosity of water, which would tend to slow down the flow of water and there-by the dispersion time of the charge into the water.

Among suitable gas-producing dissipators are mixtures of sodium bicarbonate or sodium carbonate and other water-soluble bicarbonates and carbonates with a watersoluble solid acid or acid salt which in the presence of water will react with the bicarbonate or carbonate to produce carbon dioxide gas. Such solid acids or acid salts include tartaric acid, citric acid, sodium tartrate, oxalic acid, lactic acid, the polyphosphoric acids, and boric acid.

Water-soluble binders which can be used with the selfdestructive booster explosive charge include soluble starch binders, soluble resins such as the natural gums, guar gum, locust bean gum, synthetic resins such as polyvinyl alcohol.

The cartridge container can be made in any shape desired. Usually, however, explosive cartridge containers are tubes of generally cylindrical configuration, whose open ends are closed either by crimping, or by end caps. Other useful configurations include tubes that are polygonal, i.e. triangular, rectangular, pentagonal, tetrahedral, or hexahedral in cross-section. The cartridge container should be sufficiently strong to withstand normal wear and tear prior to use, and should be moisture-resistant to prevent moisture from entering and deactivating the explosive prior to its being immersed in the water.

The opening in the cartridge container for conducting water to the compartment opens through the cartridge container outer wall and leads water to the water-expandible material. Preferably, to insure circulation of water into, and a slurry or suspension of water and explosive charge out of, the cartridge there is more than one opening in the container. When the container is to be used as a booster, which is inserted into a well in another explosive cartridge, the openings are preferably located near the top of the container, and preferably in the top end cap and in the top portion of the well. By placing the openings in such positions they are not obstructed by the walls of the well in which the container is inserted or by the fuse cap placed within its own well. When the tubular container is not to be used as a booster, it is preferred that the openings be formed around and along the side wall of the container and/or in the top and bottom ends.

When the openings are all located in a single area to avoid obstruction, as in the boosters discussed above, an enclosed passage can be provided leading from an opening to another part of the cartridge so as to increase circulation by separating the points of exposure of the water and charge. Similarly, several such passages can be provided leading from a single opening.

The openings should be of a size sufiicient to permit the passage of the water-insoluble particles of the explosive charge so they can leave the container therethrough when they are distributed in the water as a slurry or suspension. Accordingly, mesh size of the charge and the opening size should be correlated.

The openings are preferably kept closed until the cartridge or booster is to be used by a plug or a film or strip of sealing material. This can be removed manually, before immersion, or it can be of a water-soluble material which will dissolve upon immersion in water, such as polyvinyl alcohol, a Water-soluble gum, methyl cellulose, ethylene oxide polymer (Polyox) and like materials.

One simple method of sealing off the openings is to wrap a waterproof material, as a tape, around the exterior of the cartridge container. Preferably, the waterproof material is bonded to the container with an easily separable adhesive. Examples of such waterproof materials include flexible plastics such as polyvinyl chloride, polyethylene, polypropylene and moistureproof cellophane, coated woven glass fiber fabrics, and metal foils, such as aluminum foil. The tape is wrapped around and bonded to the container. In one embodiment, the tape would be ripped off from the explosive container immediately prior to use, thereby opening the openings. Alternatively, the adhesive used to seal the tape to the container could be water-soluble, so that the tape would be self-removing upon being immersed in water. Another alternative would be to use a moistureproof, water-soluble plastic film such as a polyethylene oxide (Polyox) resin film.

Protecting the explosive during storage can also be accomplished by coating the surface of the container with a water-soluble material thereby covering the openings. Such a film could serve as a moisture barrier and prevent leakage during storage, but would be dissolved away when the cartridge is immersed in water.

The self-removing film or plug will also act as an automatic timing means. By using different coating materials or adhesives having different rates of dissolution, and by applying different thicknesses of the coating material, the period before water enters the cartridge after immersion can be regulated at will.

In a prefered embodiment of this cartridge, the opening is closed, to prevent the accidental entry of moisture during storage, and is opened by the user just prior to the cartridges being immersed in water, or alternatively, shortly thereafter, by action of the water on the material closing off the opening resulting in an automatic opening atfer a predetermined period of time has elapsed.

The opening for the passage of water into the explosive charge is formed through the wall of the container, exposing the interior of the container to water when the cartridge is immersed. One such preferred embodiment is shown in FIGURE 1, where a tubular cylindrical container containing watersoluble dissipator is shown, including several openings formed through the side wall thereof. Upon immersion, water will pass through the oepnings into the interior of the container, and there contacts the explosive charge and the dissipator. The soluble dissipator will be dissolved in the water, forming gaps in the firmly packed charge and cause it to crumble, forming a slurry with, or a suspension in the water, and then passing out through the openings.

In another preferred embodiment, the dissipator is both water-soluble and gas-evolving. The gas Will aid in agitat ing the water as it enters through the openings in the container, causing mixing in the compartment, thereby decreasing the time to form a slurry or suspension and to remove most of the explosive charge from the container. In addition, if the evolution of gas is brisk enough and the cartridge container has a readily releasable cap of a type to be discussed below, the cartridge cap can be pushed out, as a result of the internal pressure exerted by the evolving gas.

Suitably in this embodiment, the container can be a tubular booster cartridge, open at one end, through which end the explosive charge including the water-activatable dissipator is poured. The open end of the cartridge is then closed off by an end cap which can be held in a loose friction fit or alternatively, bonded with a water-soluble adhesive to the container. Provision can be made for insertion of a detonator through the end cap of the container into a well formed for that purpose.

For an explosive booster cartridge container, which is normally inserted into a well in another main explosive cartridge, the openings are preferably formed in the top end cap and in the cap well, so that the circulation of water and suspended charge particles into and out of the booster is not blocked by the Walls of the main cartridge well. Such an embodiment is shown in FIGURE 2.

The cap is held in place in a fit which is sufliciently tight to prevent entry of water under normal storage conditions and to resist dislodgement, but which can be pushed out by the expansion of gas produced by the dissipator.

To facilitate the removal of the cap, and to improve storageability prior to immersion in water, the cap can be bonded to the tubular container by a Water-soluble or non water-resistant cement or adhesive such as guar gum, carboxymethyl cellulose, or a modified water-soluble starch.

Other variations will be apparent to those skilled in the art from the above description.

The container can be formed of any of the materials usually used for the manufacture of explosive cartridge containers. If plastic material is used, the container can he extruded to the desired shape, leaving an opening for filling, or it can be formed by rolling or folding a flat blank of the material to the desired shape. For example, a fiat blank can be scored, cut and folded into a cube, cone, octahedron, tetrahedron, or any tubular shape desired.

In one common method for forming a cylindrical or tubular container, the blank is rolled on a mandrel to form a cylinder, and the ends are crimped or capped and sealed. Although a tubular cartridge can be formed with a single layer of wrapping, or with many layers of wrapping, it has been found preferable to form it from at least two complete layers, up to 3 /2 layers, i.e. where up to one half of the circumference of the cylinder is formed of four layers. The methods of forming containers of different shapes are well known, and are not part of this invention. The openings can be formed by any known method and at any time during fabrication.

The container of the invention can have only a single compartment for the explosive charge combined with the dissipator. In the case of primers, a second booster charge compartment can also be provided. Another compartment or well can also be provided for a blasting cap, if desired. The relative positions of the compartments is unimportant, but the blasting cap compartment, if present, is always abutting or within the compartment containing the most readily initiated explosive.

The explosive charge is mixed with the dissipator and is preferably loaded into the container to form a firmly packed mass. Any openings are closed either by crimping the ends of the container material or by inserting end caps of known design.

The material used for forming the cartridge container is generally a strong and preferably water-resistant coated cardboard or heavy paper, such as kraft or manila of approximately sixty to one hundred forty pounds weight. Other materials suitable for use in forming cartridge containers include polymeric synthetic resin materials such as Teflon, polyethylene, polypropylene, polyvinyl butyrate, cellulose acetate, cellulose acetate-butyrate,, ethyl cellulose, polyvinyl chloride, vinyl chloride-vinyl acetate poly mer, polyvinylidene chloride, polyacrylonitrile, ethylene glycol-terephthalic acid polymers, and nylon, as well as metal foils such as aluminum.

In the preferred tubular cartridge container, the container is filled with a firmly packed granular or bonded aggregate explosive charge and dissipator and is open and closed by an end cap bonded thereto with a weak, and preferably a water-soluble, adhesive, Thus, after immersion in water the bond is destroyed, and if the internal pressure is increased by expansion of the dissipator, the cap and also the charge will readily be pushed out, exposing the charge to water.

The time required for a cartridge to be destroyed or deactivated after immersion will usually be determined by the amount and type of the dissipator, the rate at which the water enters the cartridge, the size and nature of the explosive charge particles and the manner in which the charge is packed into the container. Generally, a fastreacting gas-producing composition, rapidly increasing the internal pressure, will quickly disperse the explosive charge into the Water, and deactivate the cartridge. This will be aided by additional water-soluble material.

The rate at which the water enters and at which the dispersed charge passes out of the container will depend upon the size, number and location of the openings in the container. A large number of openings spread around the container, not blocked by any barrier, and of a size large enough to pass the explosive charge particles, would distribute the charge quickly. When the openings are located adjacent the detonator (the fuse cap in a booster or the booster in a secondary explosive charge) the cartridge will be deactivated as regards its ability to be detonated more quickly than if the openings are located away from the detonator.

The nature of the explosive charge will also have an effect on the time for deactivation. If it is firmly packed and tamped into the container, with only a relatively small proportion of a watensoluble material included, the period required to disperse the charge after water enters the container would be comparatively long. Similarly, if it is a bonded aggregate, very tightly packed, with a minimum amount of a sparingly soluble binder, the period required to disperse the charge would also be long. However, if the charge is packed loosely, with a large proportion of relatively large size soluble particles and small grains of insoluble material, the dispersion will be relatively quick. This is also true where a highly water-soluble binder is used in a bonded aggregate. Generally, the insoluble explosive grains should not be larger than will pass through an 18 mesh screen, and preferably through a 30 mesh screen.

The proportion of water-soluble material present in the charge will usually be from about 0.1 to about 20% by volume. Where an explosive material happens to be water soluble, the proportion can be even higher. Where a gasevolving composition is also present, the proportion of soluble material can be as low as 0.05% by volume, including the gas-evolving composition to the extent it dissolves.

Sufiicient gas-evolving material should be present to provide at least enough gas to vigorously agitate the water and charge to aid in mixing. More can be present to provide sutficiently brisk evolution of gas to increase the internal pressure to blow the charge out of the openings or to pop the cap off the cartridge and to blow out the charge in that manner. It has been found that between about 2 and about 20% by weight of the explosive charge is satisfactory to generate the turbulent currents for mixing the charge and water. Surprisingly, it has been found that the greater the pressure the cartridge is exposed to, the more vigorous is the evolution of gas.

This carriage can be used with any type of explosive charge. A primer will be filled with a high explosive charge. Any high explosive can be used, such as TNT sensitized-ammonium nitrate-type slurry high explosives, smokeless power-sensitized ammonium nitrate type slurry high explosives; nitrostarch-sensitized ammonium nitratetype slurry high explosives; TNT-ammonium nitrate pellet form solid high explosives and nitrostarch-sensitized ammonium nitrate-type semi-solid high explosives, containing fuels such as powdered aluminum, coal, boron and magnesium; nitroglycerine dynamites, such as semigelatins, ammonia gelatins and ammonia dynamites. The specific gravity is not critical, but should be greater than one by a sufficient amount to ensure that the cartridge will not float, even in sea water, and will preferably be at least 1.1.

A primer cartridge can include a booster explosive in close juxtaposition to the high explosive. A booster cartridge will contain a booster explosive. Any booster explosive can be used, such as pentolite (a mixture of 1:1 pentaerythritol tetranitrate (PETN) and trinitrotoluene), ammonia, dynamite, nitroglycerine dynamite, nitroglycerine, semi-gelatin and gelatin dynamites, composition B, RDX (Cyclonite or cyclotrimethylenetrinitramine) and pentaerythritol tetranitrate.

The explosive charge can be placed into the container as a slurry, and then allowed to harden. The slurrying liquid can be a water-soluble molten solid. Upon hardening, the charge is in the form of a cast stick or block. The slurrying liquid can also be a fiowable binding agent which will set upon standing, also forming a cast charge. As stated, when a gas-evolving compound is present, the slurrying liquid cannot be aqueous. The charge can also be placed into the container in particulate form, and then tamped, to ensure that it is firmly packed.

The following drawings show preferred embodiments of cartridges falling within the scope of this invention.

FIGURE 1 is an elevation view in cross-section of a tubular cartridge having openings through the sides only, with openings closed off by a water-soluble tape.

FIGURE 2 is an elevation view in cross-section of a tubular cartridge wherein the openings are through the upper cap and through the sides of the well, and are sealed with water-soluble resin plugs.

FIGURE 3 is an elevational view in cross-section of the tubular cartridge of FIGURE 2, in which the entire container is coated with a film of a water-soluble resin.

FIGURE 4 is an elevation view in cross-section of a tubular booster cartridge having openings through the top end cap only, and a passage for water leads from one of the openings into the explosive charge compartment.

The booster cartridge of FIGURE 1 is formed from a sheet 2 of weight wax-coated, water-impregnable kraft paper having openings or holes 4 punched through it. Bottom end cap 3, formed of aluminum, is inserted into and bonded to one open end of the cylinder, by an epoxy resin. The container is filled with granular explosive 5 having the following formulation, including as the watersoluble dissipator granular polyvinyl alcohol (30 mesh).

Ingredients: Parts by weight Ammonium nitrate 5.0 Nitrostarch 75.0 Ethylene glycol 5.0 Granular polyvinyl alcohol (30 mesh) 5.0 Aluminum (flake) 10.0

Top end cap 7, including well 8, is inserted into the cartridge so that the well 8 extends into the explosive charge. The cap 7 is bonded to the paper tube by a watersoluble sodium carboxymethyl cellulose adhesive.

Polyethylene tape 6 is wrapped around the side wall 2 thereby closing off the holes 4. The tape is bonded to the tube by a water-soluble sodium carboxymethyl cellulose adhesive.

Alternatively, the adhesive can be a water-insoluble material, such as a urea-formaldehyde resin glue. In this case, it is necessary to remove the tape from around the cartridge prior to placing it in the water, if it is desired to implement the self-destructive properties of the cartridge.

When the self-deactivating booster of FIGURE 1 is immersed in salt Water or fresh Water, the water-soluble adhesive holding the tape onto the container eventually dissolves, permitting the tape to fall off, and allowing the entry of water through the openings 4. The water comes into contact with the granular explosive charge and the water-soluble polyvinyl alcohol granules, and the soluble portions of the charge dissolve, leaving voids in the charge, and causing it to crumble. This permits formation of a slurry of the insoluble portions of the charge in the water and the explosive charge is then dispersed throughout the general body of water in which the container is immersed, as the water flows in and out through the holes 4. In addition, the top end cap 7 will be loosened from its bond to the container 2 when the sodium carboxymethyl cellulose adhesive is dissolved, permitting the end cap to slip off, and allowing additional water to enter at the top, and carry off the charge there.

In the booster of FIGURE 2, the cartridge 10 is formed of an extruded cellulose acetate-butyrate tube open at both ends.

Lower end cap 14 formed of cellulose acetate-butyrate is bonded across one open end of the container 15 by an epoxy cement.

A granular explosive charge 16 bonded with a watersoluble binding agent fills the tube 15. End cap 18 with blasting cap well 21 is inserted into and closes off the other end of the container 10, and is attached thereto in substantially the same manner as in the cartridge of FIG- URE 1. Holes are punched through the upper end cap 18, and the wall of well 21, and sealed with water-soluble guar gum resin plugs 19.

The booster is filled as follows. First the explosive charge in the form of a liquid slurry of the Water-soluble binding agent, the exposive charge and the dissipator is poured into the container 15, and the end cap 18 and Well 21 is then inserted. The liquid slurry charge is allowed to harden, forming the cast charge 16.

The explosive charge 16 has the formulation:

Ingredients: Parts by weight Sodium carboxymethyl cellulose 0.5 Pentolite 89.5 Sodium carbonate 5.0 Sodium tartrate 5.0

The dissipator is a mixture of sodium carbonate and sodium tartrate, 5 parts by weight of each. When the cartridge is immersed in water, the guar gum plugs are dissolved, exposing the openings and allowing water to enter the container. The water contacts the cast charge, dissolving the binder, and reacts with the gas-producing material, causing the formation of carbon dioxide. The evolution of carbon dioxide agitates the charge, as it begins to crumble from the dissolving action of the water, causing the insoluble particles to form a slurry with the Water. The turbulent action of the evolving gas sets up turbulent currents in the water, forcing the slurry out through the openings. In addition, the end cap adhesive will be dissolved, loosening the end cap, allowing it to be pushed out by an internal pressure produced by the evolving gas.

In the cartridge of FIGURE 3, the cartridge container is formed from a rolled sheet 25 of 140 Weight kraft paper impregnated with Teflon to render it Water-impermeable. Holes 27 are punched into the paper. After the holes are formed, the paper is coated with a film of polyvinyl alcohol 29 covering the paper and sealing the holes.

An end cap 30 of aluminum is permanently bonded across one open end of the container by a water-insoluble epoxy cement. An explosive charge 32 in granular form including water-soluble material and a gas-producing composition fills the container 25. Upper end cap 33 including well 34 covers the top end of the rolled sheet 25 and is bonded to the rolled sheet 25 by a water-soluble starch adhesive.

The charge has the following formulation:

The dissipator is a water-soluble gas-evolving material comprising 5 parts of citric acid and 5 parts of ammonium bicarbonate.

In the booster of FIGURE 4, the cartridge container is formed from a rolled sheet 40 of polyethylene. Lower end cap 42 of aluminum is bonded into place to close off one end of the rolled sheet 40. Perforated semi-circular tube 45 is sealed into the container so as to define a passage for water between it and the rolled tube 40 and end cap 42.

The granular explosive composition 44 is the same as in the cartridge of FIGURE 3.

Upper end cap 47 with well 48 is placed into the container so that the well 48 extends down into the charge 44 and the opening 49 is over the top end of the passage between the tube 45 and the container 40. A second opening 51 is also provided in the cap 47. Plugs 50 of water-soluble guar gum are pressed into the holes 49 and 51, sealing them.

In use, the booster is inserted into the well of another cartridge, and is submerged underwater. The upper end cap 47 faces out of the well, so that the water can readily contact and dissolve the plugs 50, and pass into the booster via holes 49 and 51. The water enters the holes 49 and 51, passes into the passage 45, and out of the perforations 55 along its length into the cartridge. Gas is evolved, and the water-souble material dissolves. A circulating current is formed flowing between the perforations 55 of passage 45 and the opening 51 and the explosive charge is carried out of the cartridge with the water.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. An explosive cartridge that exposes an explosive charge contained therein to water after immersion in water comprising in combination a container defining a compartment, an opening extending through the container into the compartment for flow of water thereinto and escape of explosive charge therefrom when the cartridge is immersed in water, and an explosive charge in the compartment including in admixture therewith a water-activatable inert dissipator which when contacted with water changes in volume in a manner to facilitate the circulation of water through the compartment.

2. An explosive cartridge in accordance with claim 1 having closure means closing off the opening to keep the cartridge watertight until use.

3. An explosive cartridge in accordance with claim 2 wherein the closure means is removable manually prior to immersion of the cartridge in water.

4. An explosive cartridge in accordance with claim 2 wherein the closure means is removable by action of water after immersion of the cartridge in water.

5. An explosive cartridge in accordance with claim 1 containing two openings spaced for circulation of water through the cartridge upon immersion in water.

6. An explosive cartridge in accordance with claim 1 including a passage for water extending from the opening to another portion of the container.

7. An explosive cartridge according to claim 1 wherein the container is tubular and the opening is located in the top end of the container.

12. An explosive cartridge in accordance with claim 11 wherein the dissipator comprises a water-soluble carbonate and a water-soluble acid.

References Cited 5 UNITED STATES PATENTS 2,759,417 8/1956 ONeill 10228X 3,279,372 10/1966 Patterson 102r 2s BENJAMIN A. BORCHELT, Primary Examiner. 10 V. R. PENDEGRASS, Assistant Examiner. 

1. AN EXPLOSIVE CARTIDGE THAT EXPOSES ANEXPLOSIVE CHARGE CONTAINED THEREIN TO WATER AFTER IMMERSION IN WATER COMPRISING IN COMBINATION A CONTAINER DEFINING A COMPARTMENT, AN OPENING EXTENDING THROUGH THE CONTAINER INTO THE COMPARTMENT FOR FLOW OF WATER THEREINTO AND ESCAPE OF EXPLOSIVE CHARGE THEREFROM WHEN THE CARTRIDGE IS IMMERSED IN WATER, AND AN EXPLOSIVE CHARGE IN THE COMPARTMENT INCLUDING IN ADMIXTURE THEREWITH A WATER-ACTIVATABLE INERT DISSIPATOR WHICH WHEN CONTACTED WITH WATER CHANGES IN VOLUME IN A MANNER TO FACILITATE THE CIRCULATION OF WATER THROUGH THE COMPARTMENT. 